======================================
| [  231.451584][   T71] ==================================================================
| [  231.452068][   T71] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [  231.452433][   T71] Read of size 1 at addr ffff8880088f469c by task kworker/u16:1/71
| [  231.452781][   T71]
[  231.452911][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  231.452914][   T71] Workqueue: netns cleanup_net
[  231.452925][   T71] Call Trace:
[  231.452928][   T71]  <TASK>
[  231.452931][   T71]  dump_stack_lvl (lib/dump_stack.c:123)
[  231.452939][   T71]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[  231.452948][   T71]  ? kobject_put (lib/kobject.c:733)
[  231.452953][   T71]  print_report (mm/kasan/report.c:483)
[  231.452957][   T71]  ? kobject_put (lib/kobject.c:733)
[  231.452961][   T71]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[  231.452966][   T71]  ? kobject_put (lib/kobject.c:733)
[  231.452970][   T71]  kasan_report (mm/kasan/report.c:597)
[  231.452976][   T71]  ? kobject_put (lib/kobject.c:733)
[  231.452984][   T71]  kobject_put (lib/kobject.c:733)
[  231.452989][   T71]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[  231.452997][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[  231.453001][   T71]  ? unregister_netdevice_many (net/core/dev.c:12241)
[  231.453006][   T71]  ? generic_xdp_install (net/core/dev.c:11630)
[  231.453010][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  231.453024][   T71]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[  231.453033][   T71]  ? netns_get (net/core/net_namespace.c:223)
[  231.453037][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  231.453046][   T71]  cleanup_net (net/core/net_namespace.c:698)
[  231.453052][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[  231.453060][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  231.453069][   T71]  process_one_work (kernel/workqueue.c:3268)
[  231.453083][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  231.453092][   T71]  ? assign_work (kernel/workqueue.c:1206)
[  231.453099][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  231.453109][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[  231.453114][   T71]  kthread (kernel/kthread.c:463)
[  231.453122][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  231.453125][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  231.453135][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  231.453141][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  231.453145][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  231.453151][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[  231.453156][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  231.453161][   T71]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [  231.483888][   T71] refcount_t: underflow; use-after-free.
| [  231.484072][   T71] WARNING: CPU: 1 PID: 71 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [  231.484386][   T71] Modules linked in: cls_matchall
| [  231.484991][   T71] Tainted: [B]=BAD_PAGE
[  231.485115][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  231.485317][   T71] Workqueue: netns cleanup_net
[  231.485494][   T71] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[  231.485704][   T71] Code: a2 b5 02 80 fb 01 0f 87 db 6e d8 fe 83 e3 01 0f 85 51 ff ff ff c6 05 c2 a2 b5 02 01 90 48 c7 c7 60 a8 c5 86 e8 72 c3 17 ff 90 <0f> 0b 90 90 e9 33 ff ff ff 48 89 df e8 20 69 a0 ff e9 ba fe ff ff
All code
========
   0:	a2 b5 02 80 fb 01 0f 	movabs %al,0xdb870f01fb8002b5
   7:	87 db 
   9:	6e                   	outsb  %ds:(%rsi),(%dx)
   a:	d8 fe                	fdivr  %st(6),%st
   c:	83 e3 01             	and    $0x1,%ebx
   f:	0f 85 51 ff ff ff    	jne    0xffffffffffffff66
  15:	c6 05 c2 a2 b5 02 01 	movb   $0x1,0x2b5a2c2(%rip)        # 0x2b5a2de
  1c:	90                   	nop
  1d:	48 c7 c7 60 a8 c5 86 	mov    $0xffffffff86c5a860,%rdi
  24:	e8 72 c3 17 ff       	call   0xffffffffff17c39b
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	e9 33 ff ff ff       	jmp    0xffffffffffffff66
  33:	48 89 df             	mov    %rbx,%rdi
  36:	e8 20 69 a0 ff       	call   0xffffffffffa0695b
  3b:	e9 ba fe ff ff       	jmp    0xfffffffffffffefa

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	e9 33 ff ff ff       	jmp    0xffffffffffffff3c
   9:	48 89 df             	mov    %rbx,%rdi
   c:	e8 20 69 a0 ff       	call   0xffffffffffa06931
  11:	e9 ba fe ff ff       	jmp    0xfffffffffffffed0
[  231.486278][   T71] RSP: 0018:ffffc900004c7a08 EFLAGS: 00010282
[  231.486486][   T71] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[  231.486719][   T71] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[  231.486971][   T71] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff0ebe134
[  231.487207][   T71] R10: 0000000000000003 R11: ffffc900004c7580 R12: 0000000000000001
[  231.487444][   T71] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[  231.487694][   T71] FS:  0000000000000000(0000) GS:ffff8880ad801000(0000) knlGS:0000000000000000
[  231.488018][   T71] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  231.488234][   T71] CR2: 00005636b0f36878 CR3: 0000000029135005 CR4: 0000000000772ef0
[  231.488468][   T71] PKRU: 55555554
[  231.488585][   T71] Call Trace:
[  231.488721][   T71]  <TASK>
[  231.488816][   T71]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[  231.488982][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[  231.489146][   T71]  ? unregister_netdevice_many (net/core/dev.c:12241)
[  231.489300][   T71]  ? generic_xdp_install (net/core/dev.c:11630)
[  231.489453][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  231.489611][   T71]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[  231.489768][   T71]  ? netns_get (net/core/net_namespace.c:223)
[  231.489938][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  231.490099][   T71]  cleanup_net (net/core/net_namespace.c:698)
[  231.490265][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[  231.490419][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  231.490592][   T71]  process_one_work (kernel/workqueue.c:3268)
[  231.490751][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  231.490922][   T71]  ? assign_work (kernel/workqueue.c:1206)
[  231.491082][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  231.491243][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[  231.491396][   T71]  kthread (kernel/kthread.c:463)
[  231.491522][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  231.491684][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  231.491863][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  231.492037][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  231.492206][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  231.492368][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[  231.492531][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)


Finger prints:
refcount_warn_saturate:netdev_run_todo:ops_undo_list:cleanup_net:process_one_work
print_report:kasan_report:kobject_put:netdev_run_todo:ops_undo_list